The present invention is in the field of deflector vanes used in the xe2x80x9cthroatxe2x80x9d portions of coal mill pulverizers.
Coal mill pulverizers, especially those of the bowl mill roller type, are typically provided with a pulverizer xe2x80x9cthroatxe2x80x9d comprising an annular air passage surrounding the pulverizer and directing an upward flow of air around the pulverizer to entrain freshly-pulverized coal particles upwardly to a classifier device. The pulverizer throat is typically provided with a plurality of angled deflector vanes which impart a spiral direction to the air flow to better assist the classifying function. Pulverizer throats come in both stationary and rotating types.
The deflector vanes themselves are often fixed in place, although adjustable vanes have been developed which allow the air passages between the vanes to be adjusted as to flow area and angular orientation.
The coal originally fed into the pulverizer is often pre-classified using known sortation machinery to eliminate debris such as rock and scrap or xe2x80x9ctrampxe2x80x9d iron. Occasionally, however, heavy debris such as tramp iron is fed into the pulverizer and collides with the deflector vanes in the throat. If the debris is big enough, the vanes can be damaged and even broken off.
The present invention is a spring-loaded, deflectable deflector vane which, under suitably forceful impact by large pieces of debris, momentarily deflects to absorb the shock and then springs back into position.
In a first embodiment a vane is pivotally mounted in the pulverizer throat on an axis permitting it to rotate downwardly and outwardly. A torsion spring has one end secured to the lower side of the deflector vane, and the other end secured to a fixed location such as the inner ring or xe2x80x9cracexe2x80x9d of the pulverizer throat. When a large piece of debris strikes the upper surface of the vane, the vane is momentarily forced downwardly and outwardly against the force of the spring, letting the impacting piece pass to the lower mill reject (pyrite) area, and thereby producing a resistive force which returns the vane to its normal position after the collision.
In a second embodiment the vane is supported in the pulverizer throat on the axis of a horizontal tubular coil spring which has an outer end connected to the vane and an inner end secured to the pulverizer throat or other fixed structure in close association with the vane. The spring is sufficiently rigid to function as a vane support during normal vane operation. Debris striking the vane causes it to deflect downwardly and outwardly as the axis of the normally rigid tubular vane support is bent.
Although torsion and coil springs are preferred, other types of spring such as leaf springs and spring equivalents could be used in the invention to provide a normally rigid vane support capable of yielding to sharp blows and then forcing the vane back to its usual position.
The vane is preferably mounted to a radially inner portion of the throat to deflect downwardly and outwardly. Whether the deflection can be described as more downward or more outward will depend on the shape and angular orientation of the vane in its rest position. It will be understood that xe2x80x9coutwardxe2x80x9d is to be understood relative to the portion of the throat on which the vane is mounted.
These and other features and advantages of the invention will become apparent on a further reading of the specification, in light of the accompanying drawings.